Keeping links in PDF attachments imported into EMPOWER

We have an application (Extream Designer) that creates an EMPOWER document to which we upload PDF attachments.

While the attachments do render fine in both preview and fulfillment, clickable links in the uploaded attachments are converted in plain text. They still LOOK like the original link, but they a re no more "linked" and thus cannot get clicked.

I assume there is some setting that "deactivates" foreign links, right?

How do we get the attachment included "as is", with working links? No need to "process" the attachments, just add the pages to the output. We do care of the content already ;-)